Pplanes fall apart as they spawn on the runway - Getting desperat.. where is my spaceglue!

[DannerD3H]

Hey KSP forum!
I have been playing KSP for a couple of years, neatly avoiding the VHB. Building some quiet amazing structures like  big space stations and mun base and such..

Well i went and fell in love with SSTO's so i thought okei lets learn to use the VHB. I build a small plane, flies like a dream, then went big and build a massive (mark IV) turbo prop science plane that flies like a dream (but slow though, and only atmospheric):

But hey i felt ready to build a SSTO after watching a number of videos. I know i might be ambitious starting out with a mark IV SSTO as these things are massive. However i want it to haul big cargo in orbit so they need to be big. My problem isn't getting in orbit (not yet) my problem is simply creating a plane that doesn't fall apart or blow up before i even start a engine..

I have had serious problems with fuel tanks mounted on the side of my fuselage just falling of like i didn't even use tape to fix it. Even though i used struts! Sometimes in both sides sometimes only one of them.. no matter if the landing gears were mounted on them or the fuselage.
Well if i design around this and actually get in the air my wings (one piece with procedural wings now) are flapping like a hummingbird and my elevons are pivoting around there center point around axial direction like its about to be ripped off..
Okei i got so tired of this that i started to try and copy other peoples planes like this one(which is really cool):

Thinking okei if i build that without any cargo it should at least stick together and be able to spawn on  the runway.. but no. the fuel tanks along the fuselage just drops of as soon as the plane loads to the run way..
Or.... everything just explodes..

WHAT THE HELL AM I DOING WRONG!?? I cant even copy other peoples work..   Will post some pictures of my miserable attempts when i get home.
Is there some kind of trick to get the parts to stick together or is there a software problem? or am i simply just plain stupid? Never had these kind of problems with my plain old fashion rockets.. or small planes using only small parts.


MODS used:
Mark IV
MechJeb
Kerbal engineer
procedual wings



Any help much appreciated, almost giving up on KSP completely now..

[DannerD3H]

This is how i attach the fuel tanks. They snap onto the rear cargobay.

Looks like this, all good

Looks like this on the runway. The left one fell of first thats why it is tilted over

Now with struts. 4 on each side. 2 on top 2 on bottom

And on the runway

Now if i empty the fueltanks

They stay

 

 

 

 

 

Giving up...

Wil KJR fix this?

 

 

[Plusck]

I think it's simply that you're putting too much weight on that surface attachment.

If you look carefully at the video (notably at about 8:17), when the guy mouses over different cargo bay sections and you see which bits of craft are highlighted as "children" of those parts, the side stack of fuel tanks appears to be separated into at least two parts, connected to the second and fourth  (?? I think) cargo bays. The wings are connected in two parts too - the front section to the second fuel tank, and the rear section (most of the wing) to the rear or second-to-rear tank.

So I'd guess that the fuel tanks are simply too heavy for a single surface attachment at the rear. Struts might help. KJR should help too. Attaching them the tanks with cubic struts then clipping them in might also help. Clipping the tanks further into the body might too.

See here for an example with ore tanks:

Spoiler

 

Ore tanks have terribly weak joints. Clipping the first set solidly into the core stack lets them all hold on.

However, if I use just the default clipping with a symmetrical attachment without moving them, the weakness of the first joint makes the others move too, so they all fall off. The first tanks only just hold on:

Spoiler

And if I move them further out still, they ALL fall off:

Spoiler

 

So I'd say that you simply need to move the tanks further in to the cargo bays and they should hold on. I wouldn't attach the lowest tank first - perhaps the second lowest, to keep it relatively close to the engine and the central point for transmitting forces from the wing.

[DannerD3H]

Thank you for the reply Plusck! I tried the KJR I cant really agree with my self if i consider it cheating, but none the less IT WORKS! And to be honest that is good enough for me Finnally i got a little hope for my SSTO dream back!

Now i have the problem i kind of saw coming, I don't fully understand it though. He seem to be able to accelerate with only two valkyrie engines and 60T of cargo. I'm pretty sure the weight of my plane is roughly the same as his, but i need 5 to get decent power ratio and that is only with 10T og cargo!!
Also my plane has some serious roll instabillity problems in the lower atmosphere.. later it is not that mouch of a problem. especially not on rockets.

This is my design so far..

Around 10 T of cargo

Starting out with 20 degree climp

 

Starting to level out and gain some last speed with the valkyries (at around 700 i engage the rockets)

Trying to raise the apoapsis

430 m/s off target..

My goal is to reach 130Km orbit

 

 

Am i climbing to steep in the beginning or simply just not enough fuel?
Again thanks for advise!

[Plusck]

I would say:

1) roll instability: what part is the wing attached to? I had a problem with this a few weeks ago and discovered (thanks to some help here) that it is absolutely, absolutely vital to ensure that there is the least possible number of joints between the engines and wings to make a really solid and stable craft.

I suggested earlier starting with the second-last fuel tank (and implied, though admittedly not strenuously enough, moving it so that it clips further in to the cargo bay) and then attaching the wing to that same fuel tank. This gives only three joints total between the engines and the wing, and minimises the number of weak joints.
Seriously, I would do that if it isn't currently the case.

2) Climbing steeply to start with is never a problem, IMHO, since with jets you don't use a lot of fuel if you're going a bit slowly. What is (again IMHO) vital is to level out the flight at the optimal height to ramp up the power.

I don't know about the engines you're using, but with Rapiers I think you should be nearly level (say about 5° above the horizon) at 9-10km, as you ramp up the speed. As speed increases, power increases and lift increases, and the horizon drops away, so your flight angle will naturally rise to about 10° as you pass through the highest power output, then maybe approaching a maximum of 15° as you reach the highest airbreathing speeds and power dops away. If you have sufficient wing, you can maybe try to pitch up at that moment to get yourself a slightly higher Ap and get through the hot bits of the atmosphere quicker, but that will cost you through drag and at this stage, you want to be firmly pointing prograde as much as possible.

So I can't really say what you should be doing, but that pic where you're at 45° angle (and about 30° off prograde) at 28km seems all wrong to me.
 

[DannerD3H]

Thank you very much!!!

My wings are mounted directly on the fuselage, so there is actually only 2 links between the wings and the engines. I made the wings a bit bigger, and the canards way bigger. It got better, but I'm sure it can get even better, it is still really hard to keep a dead east course while keeping the nose up... or rather adjusting the angle.. as soon as it settles it flies straight. but boy don't maneuver more than necessary xD

Following your tip climbing quickly to get some height. Leveling out way earlier(12km instead of 17km) that allowed me to reach much higher velocity - And i made it!!! i got my 10T cargo into 130km orbit!!! Still some way to get 50-60T in orbit, i certainly didn't had enough fuel left to haul much more. Also wasn't perfectly executed when on rockets i seem to just be far off progade.. need to practice that and keep tweaking!

No you can't say what i should do, but certainly you could point me in the right direction! so Thanks a lot!

How should i avoid the high angle off prograde? should i wait til i get higher/faster or? am i simply underpowered without the rapiers? I mean when i get 1000 more science point i will unlock the rapiers and then carry 7 of those instead of the 5 valkyries and 2 mainsails.. Guess that will help with more power both in but certainly out of air-breathing mode!

Here are some beauty shots

Perfectly circularized 130 km orbit (a bit close to my stupid failed satellite drifting around.. should probably kill that thing xD)

 

Practically empty cargobay, but what the hell.. it's a start xD and a little bit of liquidfuel left for the nukes!

Project KSS gass station has begun!

Not much fuel to refuel with tough, but well.. First SSTO docked to KSS.. powerbank xD

 

Side question.. anyone knows why it gets "dark" when you open the docking port in this cockpit?

Why does some people have so many air intakes? my engines never use more than 20% of the intake air according to the flight engineer and i really don't have many intakes?

[Plusck]

Congratulations! It's strange how making orbit with just a touch more fuel left each time can be so satisfying, eh?

As for the air intakes, I've read - and noticed examples from some of the more prolific plane-builders here - that one generally needs less intakes than one might think. I imagine that people put more because it seems logical if you don't look at the numbers, or for aesthetic reasons.

[DannerD3H]

Thx! Yes indeed! however considering the low cargo i would prefer there to be more left xD
Is there any way to hide cargo resources from the resource display? lets say I'm hauling a big orange fuel tank. this shows up as extra fuel in the resource display(even though it's disabled).

Okei, just saw someone talking about using multiple intakes pr. engine.. which seems crazy.

 

[foamyesque]

I suppose it's a bit late at this point, but some things I've found in building super-heavy planes..

 

1. Always strut the terminal end(s) of a radial stack to the core. If you started the stack with a radial attachment at the front (like a sloped nosecone), strut the back. If you started at the back for some reason, strut the front. If you started in the middle, strut both ends. This keeps them from flopping around.

2. Don't overstrut. Complex strut layouts do weird things to the physics; they seem to cause a positive feedback loop of stress-passing that eventually blows up your ship.

3. Wings should be attached as close to the central stack as possible; failing that, try and spread their loading evenly, so that all your radial stacks move in the same way.

4. Large planes will want to form a U. Don't try to eliminate it; that flex often keeps your wings from ripping clean off. Be careful in mitigating it.

5. Wheel placement on large vehicles is crucial. Your nose gear should be well back of your actual nose, because you're going to need heavy duty main gear for the tail clearance, and if you have that size of nose gear at the nose, the springs will make your ship bounce. Bringing your nose gear back means it takes more of the load and gives it less of a lever for pitch bounces, both of which dampen the motion and reduce the strain on your main wheels (and hence what is transferred into the structure).

6. I don't know about the mod engines, but, in stock, my go-to ratio is one shock intake for six rapier engines. It's right on the borderline, but doing an intake droop or changing flight profiles means it never needs more air than the intakes provide. Alternatively you can add, perhaps, a pair of radial ramp intakes, which will give you some more margin. The upshot is you don't need many intakes... any more. You may have been looking at older material, before the aerodynamics changes, where the optimum way to run airbreathers was to jam on as many intakes as possible and operate them at 68km. The addition of the flight ceiling mechanics killed that.